1. Technical Field
The invention relates to an outer race for a rocker bearing or such a rocker bearing in which the outer race has an internal sliding layer and an external support layer, and in which the sliding layer and the support layer are formed from a wound compound fiber material. The invention also relates to a method for producing such an outer race, in which a sliding layer and a support layer of fibers impregnated in synthetic resin are wound on to a winding mandrel and outer races are formed from the winding body thus produced after hardening.
2. Related Art
Such a method is disclosed, for example, in DE 42 20 327. In the method disclosed there for producing rocker bearings, a winding core is used consisting of an alternating arrangement of moulded rings for forming the pan-shaped inner profile of the outer race and separating rings for forming the end faces. Synthetic resin impregnated PTFE and/or high strength fibers, wound onto the winding core, are proposed as the sliding layer material. After the winding body thus formed is hardened, and after material is removed from the outer periphery, the outer races and separating rings can be pulled off the shaft. In this method the moulded rings remain in the outer race after being pulled off the shaft, and form the inner race of the bearing. The advantage of this is that no bearing play can be set due to the production conditions and that the outer race tightly encloses the moulded ring and inner race respectively. Such a bearing tends to wear very quickly.
There are many other known methods in which the outer race and inner race are produced separately and are subsequently connected together. With these methods there is always the question of how the outer race and inner race should be joined together. DE 84 00 958 U1 proposes, for example, designing the outer race of the radial rocker bearing so that on one end face it has axially directed sprung webs which are deformed when the bearing is inserted in a housing bore, with the result that some of the outer race bears with pre-tension against the surface of the previously inserted ball and socket mounted therein. Here too there is the disadvantage that the bearing play can only be roughly set in this manner. Furthermore, the load bearing capacity of the bearing is not limited to the optimum degree due to the isolated elastic webs around the periphery.
WO 89/02542 discloses an outer race consisting of two tin pots pressed and/or welded into each other, between which the inner race is inserted. In this case the cavity enclosed between the tin pots of the outer race and the inner race is then filled with plastic. Just as in DE 42 20 327, no bearing play can be set here either. Moreover, the production process is expensive and the production accuracy small.
To solve the problem DE 20 2004 013 251 U1 and DE 10 2004 041 084 A1 propose an outer race composed of two rings. The two races are connected positively together on the end face according to DE 20 2004 013 251 U1. Either metal or ceramic is proposed as material for the outer race. In the case of DE 10 2004 041 084 A1 the rings of the split outer race are fixed radially and axially by means of a wound housing. A compound fiber material, among other things, is proposed as the material for the housing.
A further development of the method disclosed in DE 42 20 327 is disclosed in DE 295 12 317 U1. Here the winding core is further developed to the extent that the separating rings each have two opposing axially directed projections. These projections form the shape for insertion grooves in the formed outer races, which are dimensioned so that the moulded ring can be removed from the hardened outer race by rotation, whereupon the actual inner race can be inserted. Although it is possible by this method to set the bearing play individually, this method suffers from the disadvantage that the load cross-section of the outer race is reduced due to the insertion grooves. Moreover, the grooves form edges that run transversely to the direction of running, which edges may give rise to a lubricating film irregularity and hence to inadequate bearing lubrication. Finally, the risk of contamination is increased here.
DE 20 2005 005 829 relates to injection moulded bearing housings or bearing bodies of plastic in which the bearing body or bearing housing is at the same time used as a mould for the corresponding counter-rotating bodies. Just as in the case of DE 42 20 327, the advantage of this is that no bearing play can be set in this method.
DE 35 24 761 A1 points in a different direction in that it proposes an outer race which is split at one point and on whose inner face is cast a sliding bearing by means of a tool ring as a casting. To remove the tool ring, then insert the inner race, the outer race is pulled apart on the parting line and therefore bent upwards.
All the above-mentioned methods suffer the disadvantage either that the bearings cannot be produced with sufficient accuracy and are therefore produced with inadequate properties, or that the production methods in most cases require a plurality of consecutive process steps and the processing of different materials, which render the production process complicated and expensive and may limit the durability of the bearings.
The object of this invention is to overcome such disadvantages.